有关中心性发绀不正确的是
A.发绀皮肤是冷的
B.多由心肺疾病引起
C.以上都不是
D.可分为肺性发绀和心性混合性发绀
E.常见于发绀性心脏病
参考答案:A
We were having a meeting ______ suddenly someone knocked at the door. [ ]
A. because
B. when
C. as
D. while
CRH1动车组主变压器的状态由()来监控。
A.高压控制箱
B.滤波器箱
C.变流器箱
D.DCU